Multi agent radio frequency propagation simulator

ABSTRACT

A method and apparatus for simulating radio frequency propagation paths between radio frequency devices are provided. In an illustrative embodiment, the apparatus comprising a system controller for receiving and processing test data, a data sequencer configured to interact with attenuators and RF devices, and RF paths designed to simulate RF propagation paths. The method comprising steps to execute a multiple propagation path simulation based on various inputs including attenuators and electromagnetic environment inputs in accordance with various embodiments.

CROSS-REFERENCE TO RELATED APPLICATIONS

This present application is a divisional of U.S. Non-Provisional patentapplication Ser. No. 14/200,987, issued as U.S. Pat. No. 10,055,525,filed Mar. 7, 2014, entitled “MULTI AGENT RADIO FREQUENCY PROPAGATIONSIMULATOR,” and related to U.S. Non-Provisional patent application Ser.No. 14/201,011, issued as U.S. Pat. No. 10,061,880, filed Mar. 7, 2014,entitled “MULTI AGENT RADIO FREQUENCY PROPAGATION SIMULATOR,” thedisclosures of which claim priority to the U.S. Provisional PatentApplication Ser. No. 61/809,000, filed Apr. 5, 2013, entitled “MULTIAGENT RADIO FREQUENCY PROPAGATION SIMULATOR,” the disclosure of which isexpressly incorporated by reference herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The invention described herein was made in the performance of officialduties by employees of the Department of the Navy and may bemanufactured, used and licensed by or for the United States Governmentfor any governmental purpose without payment of any royalties thereon.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a multi agent radio frequencypropagation simulator (MARPS), specifically used to determineperformance of a radio frequency (RF) communications system prior toopen air range (OAR) testing. A desirable interface between multi-agentsis through ‘over the air’ RF connections which include not only theintended direct RF communications paths but also highly variablemulti-ray propagation, range attenuation, external RF influences andnear earth influence. These influences are all difficult to predict,control, and repeat in an outdoor environment. This outdoor testing, ashas traditionally been done, is extremely expensive while simultaneouslyproviding less data points than more controlled events, and the testingevents are generally not repeatable. A need exists for an ability tointerconnect multiple devices for laboratory simulation of this outdoorenvironment.

Currently in certain types of antenna design fields the correlationbetween model and simulations (M&S), hardware-in-the-loop (HITL)testing, and open air range testing has been minimal. The complexity ofopen air test ranges cannot be fully captured in modeling and simulationor in hardware-in-the-loop testing. Open air test ranges introduce manyuncontrolled variables that not only affect the performance of an RFcommunications system but also impact the quality of the test data. Anopen air test is heavily influenced by a number of factors that othertesting methods cannot completely account for, including: the ambientelectromagnetic environment (EME) an RF system is operating in; theantenna placement, including the antenna's placement as compared toother antennas; the soil properties of the location being tested in; thephysical terrain; the placement of the RF system within that terrain;multi-ray reflection signals; desirable signals; undesirable signalspropagating in the area; hostile signals that might be trying todisrupts the RF systems functionality; general system variability; andother factors.

In open air test ranges the multiplicity of the before mentionedvariables impact the quality of the data gathered from an open air test.Thus, it is difficult to determine cause and effect from open airtesting because of the many variables introduced by the environment thatcannot be completely accounted for with other testing methods.Furthermore, the results of the open air test are not repeatable, andthe phenomenology is not clear.

Thus, a need exists to reproduce open-air near-earth effects in a laband thereby be able to more fully utilize OAR testing. To furtherreproduce open-air near-earth effects a testing system needs to accountfor all donating competition to units under test as well as labequipment to simulate the same. Also, a need exists to simulate anoperational event with vehicle movement and controlled RF effects.Another need is to be able to reproduce the scalar effects with all ofthe variables for a given electromagnetic spectrum activity. Anotherneed includes creation of a HITL laboratory environment for use indevelopmental test (DT) and operation test (OT) assessments as well asbe able to take predictions for scalar effects from M&S and rapidlytransition them into a HITL environment for validation. Another need isa requirement to converge results from M&S and OAR testing. MARPSimproves RF system designs, reduces the OAR testing time, saves money inthe development of future RF system technology, improves the correlationbetween models and system performance, increases test repeatability ofreal environments, and increases the ability to test new real-worldcomplications that the RF system encounters. MARPS addresses these needsby a variety of result/effects including simulating an OAR test scenarioin a laboratory using a computer, other RF equipment, and a set ofdigitally controlled RF paths.

An RF system being tested and used does not need modifications becausethe RF signals are modified by an exemplary aspect of a MARPS systemrather than by modifying the generating RF devices themselves. Forexample, an exemplary MARPS system could be used to test a cell phonesystem in the presence of interfering signals where the cell phone beingtested is directly plugged into the MARPS system and the interferingdevices are also directly plugged into the MARPS system. Relative signalstrengths are modified, not by physically moving the RF devices or bychanging the signals by adjusting the generating RF device, but insteadby manipulating the MARPS system paths to simulate such interactions. Asa cell phone moves through an environment, signal strength of the cellphone will vary based on a multitude of variables includingobstructions, other signals present, and even ground effects. A MARPSsystem can help create a more reliable cell phone or cell phone systemby providing reproducible tests to developers without incurring thegreat expense of open air testing. Other examples of uses for a MARPSsystem would be in designing more robust police scanners, garage dooropeners, and other RF systems.

Additional features and advantages of the present invention will becomeapparent to those skilled in the art upon consideration of the followingdetailed description of the illustrative embodiment exemplifying thebest mode of carrying out the invention as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description of the drawings particularly refers to theaccompanying figures in which:

FIG. 1 is a block diagram of a RF propagation path simulator accordingto an illustrative embodiment of the disclosure;

FIG. 2 is a diagram of propagation paths of a RF propagation pathsimulator according to an illustrative embodiment of the disclosure;

FIG. 3 is a diagram of a system under test (SUT) RF propagation pathaccording to an illustrative embodiment of the disclosure;

FIG. 4 is a diagram of an EME RF propagation path according to anillustrative embodiment of the disclosure;

FIG. 5 is a diagram of a transmitter/receiver device pair RF propagationpath according to an illustrative embodiment of the disclosure;

FIG. 6 is a diagram of an embodiment of a RF propagation path simulatoraccording to an illustrative embodiment of the disclosure;

FIG. 7 is a conceptual diagram of what characteristics a control systemhas in an illustrative embodiment of the disclosure;

FIG. 8 is a block diagram of a method for characterizing RF propagationpaths according to an illustrative embodiment of the disclosure;

FIG. 9 is a diagram of data collection from an open air range testaccording to an illustrative embodiment of the disclosure;

FIG. 10 is a block diagram of a method for implementing a simulation ona RF propagation path simulator according to one embodiment of thedisclosure; and

FIG. 11 is a diagram of a RF propagation path simulator according to anillustrative embodiment of the disclosure.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments of the invention described herein are not intended to beexhaustive or to limit the invention to precise forms disclosed. Rather,the embodiments selected for description have been chosen to enable oneskilled in the art to practice the invention.

FIG. 1 shows a high-level block diagram of a path simulator 10 inaccordance with one embodiment of the invention. Path simulator 10 canbe a scalable port system that simulates RF paths that exist in areal-world environment. Exemplary path simulator 10 comprises a systemcontroller 12, a data sequencer 14, a plurality of RF path controlmodules 16, a spectrum analyzer 18, one or more SUTs 20, an EMEgenerator 22, and one or more device pairs 24.

Both exemplary device pairs 24 and SUTs 20 are meant to send and receiveRF signals. An example device pair 24 is made up of a device pairtransmitter 25 (Tx) and a device pair receiver 26 (Rx). SUTs 20 send andreceive RF signals from all other RF devices connected to path simulator10 but device pairs 24 only send and receive signals to and from SUTs 20and not from other RF systems connected to path simulator 10. In thiscase, signals of exemplary device pairs 24 do not interact with othersignals from other device pairs 24 because of the complexity of pathsimulator 10 increases exponentially with each added device pair 24 orSUT 20 and RF signals from a device pair 24 have little or no effect onany other device pair 24 connected to path simulator 10. The number ofpaths to be simulated by path simulator 10 can be reduced by orders ofmagnitude by not allowing RF signals from device pairs 24 to interactwith other device pairs 24. A SUT 20 receives signals from all otherSUTs 20, from all device pairs 24, and from EME generator 22 becauseSUTs 20 can be devices that path simulator 10 is exhaustively testing.

Exemplary data sequencer 14 is a high-speed data input/output devicethat permits a synchronous transfer of large data set from the RF pathcontrol modules 16 and other RF devices connected to path simulator 10.Data sequencer 14 receives instructions to simulate propagation pathsbetween different RF devices. These instructions can includetime-stamped attenuator values, trigger timings, desired power on targetvalues, and other commands. During an execution of an exemplary fullsimulation, path simulator 10 is completely controlled by data sequencer14 in order to achieve consistent and reproducible results from thesimulation. In this embodiment, system controller's 12 clock-rate cannotbe relied upon to be completely consistent because of disturbances thatcan be caused by running a multiplicity of processes at any given time.One embodiment's system controller 12 can generally be some type ofmulti-purpose computer that can run on systems such as, for example,LabView®. Consequently, exemplary data sequencer 14 can operate with anindependent clock-rate that allows the scenario to be executed withtiming accuracy substantially better than other operating systems couldprovide. Before an exemplary full simulation is run, hardware controlinformation is passed from system controller 12 to data sequencer 14.During an exemplary full simulation, data sequencer 14 synchronouslychanges propagation path values, by digitally controlling attenuators,at a fixed rate. Once an exemplary full simulation is complete, resultsdata is transferred from data sequencer 14 to system controller 12 foranalysis and possible processing. Data sequencer 14 can be an Agilent®34980A multifunction mainframe.

EME 22 simulates RF background noise that might be detected by SUTs 20.Background RF noise can include television station transmissions, radiostation transmission, garage door opener signals, and other RF signalsthat exist in a real-world environment. Different locations havedifferent EME signatures and EME 22 simulates the background signaturesthat can be seen by SUTs 20.

Spectrum analyzer 18 can be an analysis port that is used fortroubleshooting. Spectrum analyzer 18 can create a visual representationof power levels of one or more propagation paths of interest.Furthermore, a spectrum analyzer 18 can be connected at nearly everylocation of interest in a path simulator 10.

RF path control modules 16 form various RF paths between one or moreSUTs 20 and other RF devices such as Tx 125, Rx 126, Tx 228, Rx 229, TxN 32, and Rx N 33. RF path control modules 16 may comprise a combinationof RF splitters and combiners, RF amplifiers, and adjustable RFattenuators arranged to create individually controlled paths betweenSUTs 20 and other RF devices connected to path simulator 10. Pathscreated by RF path control modules 16 can simulate real RF paths thatcan be seen by a SUT 20. RF path control modules 16 can be designed tobe modular, interchangeable, and independent from each other to allowpath simulator 10 to be expandable. RF path control modules 16 arebuilding blocks that can be rearranged to simulate any number RF pathsbetween SUTs 20 and the other RF devices connected to path simulator 10.

FIG. 2 shows a possible configuration of RF path control modules 16 in apath simulator 10. SUT paths 40, EME path 42, transmitter device pairpaths 44, and receiver device pair paths 46 comprise a possibleconfiguration of RF path control modules 16. Each exemplary RF pathcontrol module 16, regardless of its type, terminates in a coaxialconnection that allows easy adjustment of the hardware of path simulator10. Coax cables can be used to connect various RF path control modules16 together in various combinations. Furthermore, additional RFcomponents devices such as RF attenuators and RF amplifiers can beconnected to RF path control modules 16 to ensure that the combinationof propagation paths works correctly. For example, attenuators andamplifiers might be connected to an end of a RF path control module toincrease reverse isolation or ensure impendence matching for connectedtransmission lines.

FIG. 3 shows a possible configuration of a SUT path 40. At one end ofSUT path 40 is 4-way power divider 50. 4-way power divider 50 aggregatesa plurality of RF signals either being received by a SUT 20 or beingtransmitted by a SUT 20. A 4-way power divider can be an AeroflexWeinschel® model 1550A or model 1594 4-way resistive power divider.Connected to 4-way power divider 50 is an amplifier 52. With powerdividers there can be an insertion loss associated with the combiningand dividing of RF signals. Amplifier 52 boosts signals going to andfrom 4-way power divider 50 to keep the signal strength at proper anddesired level. End 56 of a 2-way power divider 54 connects a SUT 20 toamplifier 52 and another amplifier 57 is connected at end 55 of the2-way power divider 54. Also connected to amplifier 57 is a 4-way powerdivider 58. Amplifier 57 and 4-way power divider 58 are adapted toaccount for insertion loss and to divide and combine the RF signals. SUTpath 40 is a modular and generic propagation path that can be modified,reproduced, expanded, and moved as desired. This embodiment of SUT path40 can only connect to eight separate RF signals but certainly such amodular system can be adjusted to allow SUT 20 to connect to more RFsignals. For example, 2-way power divider 54 can be replaced by a 4-waypower divider, effectively doubling the number RF signals SUT 20 caninteract with.

FIG. 4 shows a possible configuration of an EME path 42. EME generator22 connects to end 60 of EME path 42. Amplifier 62 then boosts the EMEsignal to compensate for insertion losses resulting from dividing theEME signal with 2-way power divider 64. In this embodiment of theinvention, EME path 42 is connectible to two different SUTs 20 throughend 66 and end 68. EME path 42 is easily expandable to be connectible tomore SUTs 20 or other RF devices as desired.

FIG. 5 shows a possible configuration of a transmitter device pair path44 or a receiver device pair path 46. End 70 of transmitter device pairpath 44 is configured to connect to a transmitting device. An amplifier72 then boosts a signal from the transmitting device. Next, attenuator73 and attenuator 74 adjust a signal to a desired level. Attenuator 73and attenuator 74 are adapted to be digitally controllable by datasequencer 14 during a simulation to ensure that a signal mimics adesired RF signal. Finally, an amplifier 75 boosts a signal to accountfor losses in the connections between paths before transmitter devicepair path 44 terminates at end 76. End 76 is adapted to connect to a SUTpath 40. In an embodiment of the invention, the architecture for areceiver device pair path 46 is substantially similar to thearchitecture of transmitter device pair path 44 except that end 70 isconfigured to connect to a receiving device.

When combining multiple RF path control modules 16 into a path simulator10, RF path control modules 16 should be isolated from each other suchthat the operation of one RF path control module 16 does not interferewith the operation of another RF path control module 16. Two keyparameters in the exemplary design of the path simulator 10 are sneakpaths between RF path control modules 16 and power on target.

Sneak paths are unexpected paths from any point in path simulator 10 toany other point in path simulator 10. Reverse isolation is used by thecircuitry of path simulator 10 to restrict how much RF energy canproceed down an RF path in an undesired direction. Amplifiers not onlyamplify signals to compensate for losses in path simulator 10 they canalso to implement reverse isolation by attenuating signals passing fromthe output port of an attenuator towards the input port of anattenuator. The attenuation of signals presented to an output port of anattenuator creates a form of reverse isolation. In addition to trying toprevent sneak paths from forming by going down the wrong RF path controlmodules 16, other sneak paths must be carefully monitored and controlledto prevent RF coupling between paths that reduce the fidelity of thedata output from path simulator 10.

Power-on-target is another consideration when combining multiple RF pathcontrol modules 16 into a path simulator 10. Power-on-target is theamount of RF energy either a SUT 20 or a device pair 24 receives fromany of the other SUTs 20 or device pairs 24. Since SUTs 20 can belocated as close as a half meter away from each other, power-on-targetcan be a significant component of recreating high fidelity real worldtest because many of the RF systems being tested might see a largeamount of power-on-target.

The embodiment of a path simulator 10 found in FIG. 6 is adapted tosimulate RF propagation paths between a SUT 80, EME 82, a transmitterdevice pair 85, and a receiver device pair 86. Spectrum analyzer 88 andspectrum analyzer 89 can be placed at a number of locations in thehardware to monitor RF power levels and responses. SUT 80 is connectedto a two-way power divider 90 that allows a spectrum analyzer 88 tomonitor a SUT signal 92. A high-powered attenuator 94 can then attenuateSUT signal 92 creating SUT signal 96. Since SUT 80 can be a high-poweredRF system, such as a jammer, and signals from such systems can burn-outcomponents of path simulator 10, high-powered attenuator 94 is useful toreduce SUT signal 92 to protect components later in path simulator 10.

EME 82 generates EME signal 98 that is passed to attenuator 100 andbecomes EME signal 102. Transmitter device pair 85 generates Tx signal104 that is sent to a two-way power divider 93 that splits the signalinto Tx signal 106 and Tx signal 108. Tx signal 106 passes through anattenuator 107 to become Tx signal 110 and Tx signal 108 pass through anattenuator 109 to become Tx signal 112. Two-way power divider 91combines EME signal 102 and Tx signal 110 into interference signal 114,which is then passed to a directional coupler 116. Directional coupler116 can send interference signal 114 to be seen by SUT 80 and it cancombine SUT signal 96 and interference signal 114 to create SUT signal97. Next, SUT signal 97 passes through an attenuator 119 and becomes SUTsignal 118 and passes through another directional coupler 117.Directional coupler 117 combines SUT signal 118 with Tx signal 112 tobecome signal 120. Two-way power divider 121 allows spectrum analyzer 89to monitor signal 120 before it passes through an attenuator 123 andbecomes signal 122. Signal 122 is seen by receiver device pair 86.

FIG. 7 shows a possible configuration for a system controller 12. Systemcontroller 12 is adapted to provide a user interface 140, a data inputport 142, a control software package 144, and a hardware interface 146.In an embodiment of the invention, system controller 12 is a MicrosoftWindows based computer capable of running National Instruments LabVIEW®2011 program, with instrument communication and network access via anEthernet connection, but certainly other designs of system controllers12 are encompassed in the scope of the disclosure. User interface 140can be a graphical user interface that can allow manual data entry andcontrol of path simulator 10. User interface 140 can be further adaptedto provide monitoring capabilities of path simulator's 10 operation of asimulation. Data input port 142 can be a USB connection, an opticaldrive, a keyboard, a floppy disc, a zip drive, or any other type of datatransfer medium. Hardware interface 146 can be adapted to interface witha number of different types of hardware including a data sequencer 14,device pairs 24, spectrum analyzer 18, and any other RF device connectedto path simulator 10.

Control software 144 serves as the user interface and control system forpath simulator 10 and can have a number of characteristics. Controlsoftware 144 is adapted to accomplish data importing 150 and dataformatting 152. The data importing 150 and data formatting 152 of largefiles of RF path data can be difficult. Input data is generally in theform of RF absolute power levels or power loss points coupled withtimestamps and position data. Input data may also include timings forexternal device triggering and response data to allow for comparisonwith source data and positional analysis of response data. Input datamay be measured RF data from some type real-world test, simulated datafrom modeling software, or it may be a mixture of simulated and actualtest results. Often input data can exceed the memory capacity ofassociated hardware components, such as data sequencer 14, and thereforedown-sampling may be required to match the data with the memorycapabilities of path simulator hardware. Control software 144 can alsocalculate attenuator values from input RF data. When simulating a RFpropagation path in path simulator 10 attenuator values are importantand control software 144 can be adapted to calculate attenuator valuesfrom input data.

Control software 144 is further adapted to provide data editing 154.User interface 140 displays input simulation data, in a variety offormats, to a user and allows for a user to edit the data before andafter running a simulation. Editing may be performed on discrete values,offsets, or fixed values of any propagation path.

Simulation control 156 is another characteristic of control software144. A simulation may be run at real-time speed, at a different speed,or in a stepped mode. Simulation control 156 can allow an operator totrigger external RF devices and test equipment synchronously with thescenario playback, retrieve and display external device response data,and save and recall previously processed or edited scenario data.Simulation control 156 can also be preprogrammed where control software144 runs an entire simulation without user interaction.

During an exemplary full simulation, path simulator 10 is controlled bya data sequencer 14, which operates independently of system controller12. The control software 144 is adapted to upload 158 instructions for afull simulation to data sequencer 14 and other hardware prior to runninga full simulation. Simulation upload 158 allows control software 144 toload a full simulation into data sequencer 14, begin execution, andlater download the results from the full simulation.

Exemplary control software 144 provides data storage 160 for all typesof data involved in running a simulation. Data storage 160 includesstoring input data, storing reformatted input data, storing attenuatorvalues, and storing results data. After a full simulation has been runcontrol software 144 provides for storage and retrieval of fullsimulation and test result data. Data can include location dataassociated with different EME factors or signals including recorded datathat includes recorded signals and associated location data within anEME. Data storage 160 maintains the input data's relationships betweenRF data, timestamps, and positional information established when thedata originated. In an embodiment of the invention, the preferred storeddata format is a tab-delimited file. A tab-delimited file allows forscenario adjustments and test result data post processing by externalapplications and tools. In an embodiment of the invention both thenormalized and raw data file can be saved to allow for repeatedexecution of the saved scenario while the characterization data isvalid. Saving the scenario also allows for updated characterizations andnormalizations as needed.

Exemplary control software 144 uses input data to determine the RFpropagation characteristics for each individual RF propagation path.Characterization 162 of RF propagation paths can be an important step indeveloping a simulation with high fidelity to a known RF signal becausecomponents can all react differently. Characterization 162 minimizes thediscrepancies in a simulation caused by variation in hardware componentsof the path simulator 10. During characterization 162 the centerfrequency of operation for each RF path is calculated and the RFpropagation properties for each path are measured. FIG. 8 shows steps toaccomplishing characterization of a RF propagation path. Step 210 can beconnecting a spectrum analyzer at one end of a RF path and a signalgenerator at another end of the RF path. Step 212 involves determiningthe center frequency of operation for the path RF path in question.Next, as in step 214, the signal generator is set to input the centerfrequency into the RF path. In step 216 the input signal is initiated.While the input signal is transmitting, attenuators in the RF path arestepped through their full range of values, as in step 218. Using aspectrum analyzer, the response of the RF path is measured in step 220.Finally, in step 222 a characterization array is created with all of thepertinent values to all of the RF propagation paths responses to thecenter frequency that will be used during a full simulation.

Referring back to FIG. 7, control software 144 also includes tools totrigger external devices as part of a simulation. Triggering events 164may be assigned by time or be scenario steps, with delays and start andstop times also selectable. In an embodiment of the invention, triggersfor all devices are independently programmed.

Furthermore, control software 144 monitors 166 response data fromexternal devices, e.g., devices simulated by the EME system, capturedduring scenario execution and monitors 166 results from a simulation runon path simulator 10. Data from external devices, including devicessimulated by the EME system, can be stored synchronously with testresult data collected. Both trigger data and trigger response data issaved in control software 144 output file, along with the inputtimestamp and position data. Monitoring 166 of trigger response data andtest result data provides valuable information regarding the SUTs beingtested.

In an exemplary embodiment of the invention, input data for pathsimulator 10 is collected from an OAR test. Generally, path simulator 10is meant to simulate an OAR test in a laboratory through electricalhardware. Being able simulate an OAR test in a laboratory can reducedevelopment costs by allowing researchers to test adjustments toequipment without going to the expense of a full OAR test. A fullsimulation is used to duplicate range test conditions for some type ofRF system. Path simulator 10 can simulate conditions where the RF systemin question can be fixed in its position or it can be moving within anEME that relates locations and recorded or specified EME signals, forexample. For example, the RF system might be attached to a movingvehicle. FIG. 9 shows how an OAR test can be simulated using datacollected from said OAR test. In a type of OAR test that path simulatorcan reproduce, SUT 230 is connected to vehicle 232 and vehicle 232 ismoving down path 234. Contributing to what RF signals SUT 230 detects isEME emissions 236, a transmitter 238, and a receiver 240. To recreatethis environment in a laboratory RF paths 242 are measured and storedwith time-stamped information, and positional information attached. Thedata collected can become input data for path simulator 10, which canthen use digitally controlled attenuators to recreate the RF paths 242from the OAR test. During a simulation in path simulator 10, RF pathattenuators can be controlled in such a way that the movement of thevehicle 232 and the RF paths' 242 relationships with the other RFsignals can be recreated.

FIG. 10 shows a possible method for implementing a simulation using apath simulator 10. In step 250, input data is provided to path simulator10. Path simulator input data includes a time-stamped list of measuredor calculated RF received power measurements and associated geographicalposition data for all RF systems involved in a simulation. Input datacan be a set of parameters detailing RF power propagation between alltransmitting devices and all receiving devices used in a particular testscenario. Next, in step 252, the input data is down-sampled and atime-stamped list of calculated path loss values called a link budgetarray is created. Down-sampling can be necessary because systemcontroller 12 and data sequencer 14 cannot always handle the amounts ofdata collected from an open air range test or from modeling andsimulation software. In an embodiment of the invention, the link budgetarray is stored as an array of LabVIEW® clusters. A link budget arraycan have one element for each step of a full simulation, and values ofeach element of a link budget array are fixed values.

Using the input data, a center frequency of each RF propagation paththat will be used in a simulation is determined in step 254. Next, afrequency array is created in step 256. A frequency array defines thecenter frequency of the signal that is to be simulated on each path.Next, in step 258 the frequency array is used to characterize each RFpropagation path to be used in a simulation and create acharacterization array. A characterization array is an array of valueswhich are used to determine the actual path loss of each RF propagationpath for all attenuator settings. The characterization array containsmeasured path loss/gain settings for all paths used in a simulation. Instep 260, the characterization array is applied to the link budgetarray. In this process, the link budget path loss values are replacedwith the nearest match from the characterization array, producing acontrol array, which is a normalized version of the link budget array.The control array contains values for RF propagation attenuators andother hardware that correct for imprecision in path simulator hardwareand connections between test devices and path simulator hardware.

After a control array is prepared, a full simulation can be executed toverify correct RF propagation path reproduction, as seen in step 262. Inthe event that errors in received power and propagation path valuesoccur, correction factors may be applied to the control array in step264. Correction factors that have been applied can be saved for lateruse including use after new characterizations are applied to the controlarray.

Next, triggers are added to the control array in step 266. Triggers areused to activate a SUT, an external device, or external test equipment.Triggers may be specified by time or by step number in a scenario. Thecontrol array with triggers added is then uploaded to a data sequencer14 in step 268 for the simulation to be executed in the hardware in step270. Finally, in step 272 the results from a full simulation aremeasured and recorded to be used in later analysis.

FIG. 11 shows another embodiment of a MARPS system 280 comprising asystem controller 282, a data sequencer 284, a SUT 286, an EME generator288, a first RF device 290, and a second RF device 292. The systemcontroller 282 is adapted to receive input data 296 and then processsaid input data such that an output data set is created. Input data 296can comprise measured power levels and losses of radio frequency signalsmeasured during an OAR test or a modeling and simulation environment.Output data can comprise a modified set of the input data adapted tointerface with attenuators and other electrical components in the MARPSsystem 280 used to simulate propagation paths and values for radiofrequency signals. Data sequencer 284 is connected to system controller282 and is adapted to receive said output data from system controller282. Data sequencer 284 then translates the output data from systemcontroller 282 into a first, a second, a third, and fourth plurality ofpath instructions, and a first, a second, a third, and a fourthplurality of device trigger instructions.

MARPS system 280 found in FIG. 11 further comprises a SUT path 302, anEME path 304, a first device path 306, and a second device path 308. SUTpath 302 can be connected to the SUT 286 and to a power divider/combiner330. Connecting SUT path 302 to data sequencer 284 is a first pathconnection 310 which relays the first plurality of path instructionsfrom data sequencer 384 to SUT path 302 to modify the attenuator valuesof SUT path 302 and thereby modify a SUT signal to a desired level. EMEpath 304 is connected to EME generator 288 and to power divider/combiner330. Connecting EME path 304 to data sequencer 284 is a second pathconnection 312 that relays the second plurality of path instructionsfrom data sequencer 384 to EME path 304. The second plurality of pathinstructions can modify the attenuator values of EME path 304 andthereby modify a background noise signal generated by EME generator 288.The modified background noise signal can be substantially similar to ameasured background noise signal obtained from either an OAR test ormodeling software. First device path 306 is connected to first RF device290 and to power divider/combiner 330. Connecting first device path 306to data sequencer 284 is a third path connection 314 which relays thethird plurality of path instructions from data sequencer 384 to firstdevice path 306. The third plurality of path instructions can be used tomodify the attenuator values of first device path 306 and thereby modifya first device signal generated by a first RF device. The modificationmay be such that the first device signal is substantially similar to ameasured first device signal obtained from either an open air range testor modeling software. Second device path 308 is connected to second RFdevice 292 and to power divider/combiner 330. Connecting second devicepath 308 to data sequencer 284 is a fourth path connection 316 whichrelays the fourth plurality of path instructions from data sequencer 384to second device path 308 to modify the attenuator values of seconddevice path 308. The modified attenuator values may further modify asecond device signal generated by a second RF device such that thesecond device signal is substantially similar to a measured seconddevice signal obtained from either an open air range test or modelingsoftware.

A first trigger connection 322 connects SUT 286 to data sequencer 284,which relays the first plurality of device trigger instructions to SUT286. A device trigger instruction includes commands about when thedevice is supposed to be powered on, transmitting, and when the deviceis supposed to power off. Through a combination of trigger commands andattenuator instructions a SUT's signal strength can be adjusted to thedesired level. A second trigger connection 320 connects EME generator288 to data sequencer 284 and relays the second plurality of devicetrigger instructions from data sequencer 284 to EME generator 288. Athird trigger connection 324 connects first RF device 290 to datasequencer 284 and relays the third plurality of device triggerinstructions from data sequencer 284 to first RF device 290. A fourthtrigger connection 326 connects second RF device 292 to data sequencer284 and relays the fourth plurality of device trigger instructions fromdata sequencer 284 to second RF device 292. The second, third and fourthtrigger connections controls the respective connected RF device and incombination with attenuator instructions controls the signal strength ofan RF signal being input into the MARPS system.

Although the invention has been described in detail with reference tocertain preferred embodiments, variations and modifications exist withinthe spirit and scope of the invention as described and defined in thefollowing claims.

The invention claimed is:
 1. A multiple radio frequency path simulatorapparatus comprising: a system under test path connected to a pluralityof other radio frequency paths and adapted to interact with a systemunder test; an electromagnetic environment path connected to the systemunder test path and adapted to transfer background noise signals; afirst device path connected to the system under test path and adapted totransfer a first device signal; a second device path connected to thesystem under test path and adapted to transfer a second device signal; asystem controller adapted to receive a first dataset and output a seconddataset, wherein the first dataset comprises measured or user definedpower levels and losses of radio frequency signals and the seconddataset comprises a modified set of the first dataset adapted tointerface with attenuators and other electrical components to simulatepropagation paths and values for radio frequency signals; and a datasequencer connected to the system controller adapted to receive saidsecond dataset from the system controller; wherein, the data sequencertranslates the second dataset into a first, a second, a third, and afourth plurality of path instructions, and wherein the data sequencerfurther translates the second dataset into a first, a second, a third,and a fourth plurality of device trigger instructions; wherein, thefirst plurality of path instructions sets attenuator values of thesystem under test path and thereby modifies a system under test signal,wherein a second plurality of path instructions sets attenuator valuesof the electromagnetic environment path adapted to modify a firstbackground noise signal generated by an electromagnetic environmentgenerator such that the first background noise signal is the same as ameasured or user defined second background noise signal, wherein thethird plurality of path instructions sets attenuator values of the firstdevice path adapted to modify the first device signal generated by afirst radio frequency device such that the first device signal is thesame as a first test signal measured by a system under test, wherein thefourth plurality of path instructions sets attenuator values of thesecond device path adapted to modify the second device signal generatedby a second radio frequency device such that the second device signal isthe same as a second test signal measured by a system under test;wherein a first plurality of trigger instructions turns on a systemunder test at discrete times, wherein a second plurality of triggerinstructions is adapted to turn on the electromagnetic environmentgenerator at discrete times; wherein a third plurality of triggerinstructions is adapted to turn on the first radio frequency device atdiscrete times, and wherein a fourth plurality of trigger instructionsis adapted to turn on the second radio frequency device at discretetimes.
 2. The radio frequency path simulator apparatus of claim 1,wherein the first dataset comprises measured power levels and losses ofradio frequency signals that were obtained from an open air range test.